PCB Signal Integrity Tool

Transmission Line Loss Calculator

Calculate conductor loss, dielectric loss, and surface roughness effects for microstrip and stripline structures

Line Parameters

Enter your transmission line geometry

Geometry
mm
mm
mm
mm
Geometry
mm
mm
mm
mm
Material Properties
Conductor & Surface
µm
Frequency
GHz
GHz

Loss Components

Total transmission line loss consists of:

  • Conductor Loss (αc): Due to finite conductivity and skin effect
  • Dielectric Loss (αd): Due to polarization losses in substrate
  • Roughness Loss: Additional loss from surface roughness (Hammerstad-Jensen model)

Loss Analysis Results

At operating frequency

Total Loss
--dB
Total attenuation over trace length
Loss per Unit Length
--dB/mm
-- dB/inch
Conductor Loss (αc)
--dB
Skin effect + DC resistance
Dielectric Loss (αd)
--dB
Substrate polarization loss
Roughness Loss
--dB
Hammerstad-Jensen correction
Characteristic Impedance
--Ω
Estimated Z₀
Skin Depth
--µm
At operating frequency
Effective εr
--
Effective dielectric constant

Loss Distribution

Conductor
Dielectric
Roughness
Conductor: --%
Dielectric: --%
Roughness: --%
Loss vs. Frequency
Frequency (GHz) Loss (dB)
Total Loss
Conductor
Dielectric

Microstrip Cross-Section

Ground Plane Dielectric Substrate (εr) W H

Loss Calculation Formulas

Conductor Loss (Microstrip)

αc = Rs / (W × Z₀) [Np/m] Rs = √(π × f × μ₀ / σ)

Rs is surface resistance, W is trace width, Z₀ is impedance, f is frequency, σ is conductivity

Dielectric Loss

αd = 27.3 × (εr/√εeff) × (εeff-1)/(εr-1) × tan(δ) / λ₀

tan(δ) is loss tangent, εeff is effective permittivity, c is speed of light

Roughness Factor (Hammerstad-Jensen)

Ksr = 1 + (2/π)×arctan(1.4×(Δ/δ)²) α_rough = αc × Ksr

Δ is RMS roughness (≈ Rz/4), δ is skin depth. Factor ranges from 1 to 2.

Skin Depth

δ = 1 / √(π × f × μ₀ × σ) Cu @ 1GHz ≈ 2.1 µm Cu @ 10GHz ≈ 0.66 µm

Current penetration depth into conductor, decreases with √f

Effective Permittivity (Microstrip)

εeff = (εr+1)/2 + (εr-1)/2 × 1/√(1 + 12×H/W)

Accounts for fringing fields in air above microstrip

Total Loss

α_total = αc×Ksr + αd [dB/length] Loss(dB) = α_total × L × 8.686

Convert from Np/m to dB/m by multiplying by 8.686 (20/ln(10))

Need a Low-Loss PCB for RF or High-Speed Signals?

Transmission-line loss depends on frequency, dielectric properties, copper roughness, trace geometry, stackup, and board length. A calculator can estimate loss, but the final PCB construction should be reviewed against the selected laminate and fabrication process.

Learn how our engineers review high-frequency materials, controlled impedance, and RF stackups before production.